Dendritic simplification and synaptic loss represent major structural correlates of dementia in Alzheimer?s disease (AD) and frontotemporal dementia (FTD). Mutations in the microtubule-associated protein tau are a major cause of FTD and increase the risk of developing AD. Mutations in valosin-containing protein (VCP) have also been linked to familial FTD. In the prior project period, we discovered that dendritic calcium dyshomeostasis, dysregulated mitophagy and altered protein phosphorylation contribute to dendritic shrinkage in several models of neurodegeneration. We also discovered a novel interaction between VCP and the neuroprotective kinase PTEN-induced kinase 1 (PINK1). VCP is a multifunctional protein implicated in protein degradation, vesicular transport and Golgi remodeling, and these functions are mediated by distinct VCP cofactors. Based on preliminary data, we hypothesize that PINK1 interacts with VCP to prevent tau- mediated dendritic shrinkage. We will utilize primary rodent cortical neurons and human iPSC-derived neurons to study quality control mechanisms that contribute to neuroprotection against tau-mediated degeneration of dendritic arbors and spines. We will also assess the neuroprotective potential of upregulating PINK1 signaling in vitro and in vivo. Completion of these studies will reveal how proteins implicated in different neurodegenerative diseases function together to protect against tau-mediated neurodegeneration.